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Thread: Charging Question

  1. #16
    Airmarshal-IL James.A's Avatar
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    [QUOTE=ebeeby;1107548]That doesn't necessarily mean that I'm right. I still do not fully understand the theory behind these things.

    To quote the Grateful Dead; "answers a plenty in the bye and bye".
    1973 R75/5

  2. #17
    Liaison 20774's Avatar
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    Quote Originally Posted by James.A View Post
    To quote the Grateful Dead; "answers a plenty in the bye and bye".
    From St. Stephen, one of my favorites!
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #18
    Heartbeat of my R100GS Guenther's Avatar
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    I think James theory is close. But if any of the BIG diodes (to B+ and from ground) would fail the output to the battery would be LOWER because the failed diode would not add its share of its alternator phase to the DC output at B+/battery.

    But there are three LITLE diodes (to D+) which independently from the big diodes should produce about the same voltage. Their output is connected to the voltage regulators input and also to one side of the GEN light. If one of these little diodes fail there would be a lower output voltage on D+. Hence the regulator 'thinks' we are below 14.0V and increases the current (DF) through the rotor. Now the big diodes (all working) generate an even higher voltage at the battery. This higher voltage on B+ is also present at the other end of the GEN light. Now we have a difference between the two sides of the GEN light and the GEN light comes on.

    And bottom line: The diode board has a fault.

    ChargingSystem.jpg

    Btw. with a stock voltage regulator (like from Hellas) and a good voltmeter you normally don't get 14+ Volts at the battery. Typically 13.70-13.85 Volts because of a voltage loss in the wire and connectors to the battery.

    /Guenther

  4. #19

    Broken connection

    Took the cover off this morning and it turns out one of the 3 alternator wires had a broken connection on the stator. Resoldered this wire and the problem went away. Thanks to all for your help!
    Charlie P.
    1992 R100R

  5. #20
    Heartbeat of my R100GS Guenther's Avatar
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    Thanks for reporting back the problem and fix. A disconnected phase cable of the alternator - same symptom as a dead big diode on the diode board.

    /Guenther

  6. #21
    Airmarshal-IL James.A's Avatar
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    Many thanks to Guenther for providing the rest of the story and the true technical explanation.
    1973 R75/5

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